Toe-heel type bindings that provide lateral heel release and which mitigate inadvertent pre-release have been proposed. However, during aggressive edging on hard-pack snow or ice, or especially in the presence of Phantom Foot or Slip-Catch events (for more information about these injury mechanisms, please refer to: Effect of Ski Binding Parameters on Knee Biomechanics; A Three-Dimensional Computational Study, Med. Sci. Sports Exerc., 2004; July; 36(7):1218-25; as well as, Kinematics of Anterior Cruciate Ligament Ruptures in World Cup Alpine Skiing: 2 Case Reports of the Slip-Catch Mechanism, Am J Sports Med, 2013 May; 41(5):1067-73; and Critical Load Cases for Knee Ligaments at Skiing—An Engineering Approach, Skiing Trauma and Safety: Thirteenth Volume ASTM STP 1397, 2000:160-74; incorporated herein by reference), those bindings with their correspondingly tall heel pads increase the effective lever arm over which the abduction force component of a Phantom Foot or Slip-Catch event acts, thereby increasing valgus torque within the knee. Excessive valgus torque within the knee causes excessive strain across the anterior cruciate ligament (ACL), excessive strain across the medial collateral ligament (MCL), excessive compressive loads on the lateral surfaces of the proximal tibial plateau, excessive compressive loads on the lateral surfaces of the menisci, and excessive compressive loads on the lateral condyles of the distal end of the femur. As such, the presence of excessive strain and compressive loading has required proposed bindings to release laterally at the heel in order to limit the strain and compressive loads. Those prior art lateral heel release bindings with their tall heel pads also have the capacity to generate large tensile loading of the ACL during Boot Induced Anterior Drawer (BIAD) events, which pure or nearly-pure BIAD-events, lateral heel release bindings cannot address. The inherently tall heel pads of those lateral heel release bindings are a consequence of the stacking-height of the lateral heel release mechanism and the longitudinal pressure spring(s). The heel pads of those lateral heel release bindings have heights of 30 mm and more when measured from the ski top surface to the upper surface of the heel pad, where the boot typically sits.
Tall heel pads extend the distance from the snow surface to the knee, thereby increasing the effective lever arm from the point at which abduction forces enter the medial edge of the ski (under, or near, the projected axis of the tibia) at the ski-snow boundary—to the center of the knee. Increasing the distance over which an abduction force generates valgus torque to the knee—together with the addition of tibia torque—increases strain across the ACL (Valgus Plus Internal Rotation Moments Increase Anterior Cruciate Ligament Strain More Than Either Alone. Med. Sci. Sports Exerc., 2011 August; 43(8):1484-91. incorporated herein by reference). Increased strain across the ACL then increases the possibility that the ACL will reach its elastic limit, causing a skier to sustain a Grade-I ACL sprain (semi-mild sprain), Grade-II ACL sprain (significant sprain); or causing a skier to sustain a Grade-III ACL rupture. ACL injuries are the most frequent injury in alpine skiing (see the peer reviewed journal paper on ski-injury epidemiology, Snowboarding Injuries: Trends Over Time and Comparisons with Alpine Skiing Injuries, Am J Sports Med, Jan. 12, 2012; published online as a preview, incorporated herein by reference) and are severe in terms of the level of debility imparted because they require at least 8-months of aggressive rehabilitation after reconstructive surgery. Recently, it was estimated that approximately 50,000 skiing-ACL injuries occurred during the 2011-12 alpine ski season at an estimated US$20,000 cost per injury, or a total accumulated cost of US$1-billion per year. The estimated US$20,000 cost per injury includes diagnosis, treatment and rehabilitation, but does not include the costs associated with the typical onset of early PTOA (post-traumatic osteoarthritis) or the social cost of worker-compensation during the course of rehabilitation. Alpine skiing ACL injuries are therefore both frequent and severe. As such, an alpine ski binding, an AT ski binding and/or a tech ski binding that is able to mitigate such injuries would be highly desirable.
There is thus a need for a ski binding that provides the benefits of lateral heel release and retention while minimizing the forces, torques and bending moments that are transferred to the musculoskeletal structures of the leg (e.g. the knee, the ACL, the MCL, the tibial plateau, the menisci and the condyles of the femur) by the lever arm from the snow surface to the knee. Similarly, the minimization of forces, torques and bending moments acting upon these musculoskeletal structures will result in a reduced number of instances whereupon the lateral heel release of a binding should be actuated.